1. Field of the Invention
This invention relates to machinery for scraping incrustations from the inner surfaces of ladles and more particularly it concerns improvements to such machinery which permit scraping to be carried out without removal of the molten contents of the ladle.
2. Description of the Prior Art
In the processing or refining of various metals, particularly non-ferrous metals, the metal is held in the molten state in a ladle. Often the ladle is provided with an electrical coil which surrounds the ladle and which receives alternating electrical current to maintain the molten contents of the ladle in a heated and agitated state. During this time impurities separate from the metal and collect near the top of the ladle in the form a floating slag which can easily be removed. A certain amount of the impurities, however, become adhered to the sides of the ladle and build up as incrustations which interfere with the proper operation of the ladle.
The most common technique used in the past to remove these incrustations involved manual scraping after the ladle was emptied of its contents. However, once the ladle is emptied and the incrustations become cooled and exposed to the atmosphere, they harden and become extremely difficult to remove. The ladle may be scraped manually while it still contains the molten metal but this is obviously a dangerous and physically exhausting procedure.
Various mechanical devices have been proposed for automatically scraping incrustations from the inner surfaces of ladles; however, these devices all have inherent problems. Specifically, they all require moveable linkages or joints in the vicinity of the ladle lining and these linkages or joints become rigid as the molten metal surrounding them solidifies. In most cases these mechanical devices are used only when the ladle has been emptied; however, as mentioned above, the incrustations become much harder and more difficult to remove after the ladle has been emptied.
Examples of previously proposed mechanical devices are shown and described in U.S. Pat. Nos. 1,862,751 to Ingraham, 3,736,615 to Kumaki, 4,095,306 to Norton, 4,210,976 to Apelt et al and 4,328,959 to Holtmann, as well as U.S.S.R. Pat. No. 647,022 to Nizhnetagil Metallu. The Ingraham patent shows a ring shaped scraper which is lowered down into a ladle by means of a chain. This device, in addition to using an articulated chain in the ladle bath, has no means for forcing the scraper elements against the ladle walls nor does it have any means for forceably scraping in the downward direction. The Kumaki patent shows a power driven impact hammer mounted under the surface of the bath in a ladle but the device requires that the ladle first be emptied of its contents and it further requires elaborate cooling means surrounding the hammer. The Norton patent shows an articulated scraper mechanism which also cannot be operated in a molten ladle bath. The Apelt et al patent shows the use of chain or mechanical link supported scraping elements forced outwardly, by centrifugal action, to the sides of the ladle. These, of course, could not operate while submerged in a bath of molten metal in the ladle. The Holtmann patent shows mechanically driven cutter blades and articulated clamp elements wich could not be used in a molten bath. The U.S.S.R. patent also shows articulated scraper legs with pivotal joints and actuator devices which are located inside a ladle and which could not be used unless the ladle has been emptied.